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Robert C. Ebel, Monte Nesbitt, William A. Dozier Jr. and Fenny Dane

The northern fringe of the Gulf of Mexico has an excellent climate for growing high-quality satsumas that are available in U.S. retail chain stores before most other citrus. In part because of high fruit quality, satsuma mandarin production grew into a major industry in Alabama, Louisiana, Mississippi, and the panhandle of Florida in the early 1900s. Freeze protection measures were not sufficient to prevent devastation of the industry by severe freezes. For the period encompassing the late 1900s, freeze risk was estimated using a mathematical approach that determined killing temperature based on air temperature. Freeze injury was determined to occur 1 out of every 4 years on average, although the freezes tended to come in clusters that have as yet not been correlated with long-term climate patterns. Within-tree microsprinkler irrigation, which was not available in the early 1900s, has been shown to reduce the severity of injury. Within-tree microsprinkler irrigation allows full production the year after the freeze, whereas unprotected trees must be grown from the base or replanted. The northerly geographical limit in the southeastern United States whereby satsumas can be successfully grown commercially is currently not known. Methods of protecting the entire tree, including overtree microsprinkler irrigation plus windbreaks and high tunnel houses, are being evaluated. More cold-tolerant satsuma cultivars have been selected, but they reduce freeze risk by at most 2 °C in this region compared with current commercial cultivars. Genetic modification is one possible mechanism for improving cold tolerance sufficiently to reduce freeze risk similar to that of the citrus industry in Florida.

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Monte L. Nesbitt, Robert C. Ebel and William A. Dozier Jr

Satsuma mandarin is presently the primary citrus crop for citrus growers in south Alabama, south Mississippi, and for certain new plantings in northwest Florida. Current growth in satsuma mandarin hectarage in Alabama is similar to the historical hectarage expansion that occurred during decades or clusters of years with a low incidence of lethal, freezing temperatures. Commercial groves currently range in size from 100 to 2000 trees and use various freeze protection strategies, including wind breaks, overstory frost protection with pine or pecan trees, under-tree and scaffold branch irrigation, and high tunnel polyethylene-covered greenhouses. The various methods of freeze protection require adjustments in cultural management practices, including spacing, pruning, irrigation, and fertilization. The primary rootstock used and recommended for its cold-hardiness and edaphic adaptation is Poncirus trifoliata. Some groves use ‘Swingle’ citrumelo, mainly because it is grown and propagated in Louisiana, where it is valued for its higher salt tolerance. ‘Owari’ was the original cultivar introduced to the United States from Japan in the late 19th century and is still the main cultivar in Alabama today, although earlier maturing cultivars, including ‘Brown Select’, ‘Early St. Ann’, and ‘LA Early’, are being introduced to extend the marketing season. Cultivars from Japan and China, including ‘Okitsu Wase’, ‘Miyagawa Wase’, and ‘Xie Shan’, are currently being evaluated for suitability in the region. Three general methods of culture with regard to spacing and pruning are discussed. Nitrogen application rates are typically low to moderate, yet leaf nitrogen levels surveyed in groves in 2005 were generally optimal or high with respect to published sufficiency levels for mature citrus in Florida.

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Robert G. Nelson, Benjamin L. Campbell, Robert C. Ebel and William A. Dozier Jr.

This article reviews the results of 5 years of marketing research on Alabama satsumas and makes recommendations for future progress. Although there are only 28 ha of satsuma orchards in production in Alabama at this time, there are a number of encouraging developments that suggest considerable potential for expanding the industry such as microsprinkler freeze protection, new early-maturing and cold-tolerant varieties, contract sales through the Farm-to-School Program, and rising demand for premium mandarins. Prospects for the industry marketing effort are considered from the perspectives of analyzing marketing opportunities, identifying market segments, selecting attractive target markets, designing marketing strategies, planning marketing programs, and managing the continuing marketing effort. A number of distinct consumer segments have been identified, including one that prefers fruit that is still slightly green and another that prefers a longer shelf life. A peeled-and-sectioned product also appears to have considerable market potential. Name recognition is still a problem as is insipid flavor from fruit that is marketed beyond its optimal ripeness. Needs for the future are detailed and include the needs of the commodity (freeze protection and expanded acreage), the needs of the market (consistency and quality), the needs of the product (quality standards and consumer awareness), the need for and the needs of a brand (recognition and equity potential), the needs of an organization (cooperation and leadership), and the needs of the industry (processes for building equity, forestalling competition, reducing supply shocks, and attracting investment).

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James F. Hancock and Charles Stuber

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Xinwang Zhang, Ikuo Nakamura and Masahiro Mii

Wild species and cultivars of Petunia were subjected to analysis for clarifying the historical progenitors of garden petunias (Petunia hybrida) using polymerase chain reaction–restriction fragment length polymorphism (PCR-RFLP) of Chalcone synthase J (Chs-J) gene. The PCR products for Chs-J intron with adjacent part of exons digested with RsaI enzyme revealed that P. integrifolia and P. inflata (P. integrifolia complex), both with purple flowers, had one large-sized band [650 base pairs (bp)], whereas P. axillaris (P. axillaris complex), a white-flowered species, showed two smaller-sized bands (200 or 280 bp and 350 bp). In P. axillaris, two different band patterns were found among the three subspecies: 200 and 350 bp for P. axillaris subsp. axillaris and 280 and 350 bp for P. axillaris subsp. parodii and subsp. subandina. The 200-bp band was revealed to be specific to P. axillaris subsp. axillaris. P. hybrida cultivars showed four different band patterns, each of which consisted of two to three of the four bands (200, 280, 350, and 650 bp) detected in the wild taxa examined. These results indicate that the wild species analyzed here might partially have contributed to the Chs-J gene of garden petunias analyzed and demonstrate the use of PCR-RFLP in establishing relationships among closely related species and cultivars of Petunia. The puzzling problem related to the possible contribution of more than one subspecies of P. axillaris is discussed.

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Sergio Jiménez, Jorge Pinochet, Anunciación Abadía, María Ángeles Moreno and Yolanda Gogorcena

The use of rootstocks tolerant to iron deficiency represents the best alternative to prevent Fe chlorosis for peach production in calcareous soils. Early detection laboratory screening procedures allow the selection of new Fe-efficient rootstock genotypes. Seventeen Prunus rootstocks were tested for root ferric chelate reductase (FC-R) enzymatic activity, leaf SPAD values, and field performance. Some rootstocks were used as a reference to compare with new Prunus selections. Micropropagated plants were grown in hydroponic culture with half-strength Hoagland's nutrient solution containing 90 μm Fe(III)-EDTA as a control treatment. Plants were transferred to iron-free fresh solutions for 4 days and were thereafter resupplied with 180 μm Fe(III)-EDTA for 1 or 2 days. In vivo FC-R activity was measured in all treatments, i.e., control, Fe-deficient, and 180 μm Fe(III)-EDTA resupplied plants. The FC-R activity after Fe resupply was higher in Fe-efficient genotypes such as AdesotoPVP, FelinemPVP, GF 677, Krymsk 86™, and PAC 9921-07 than in the controls. No induction of FC-R activity was found in other genotypes such as Barrier, Cadaman™-AvimagPVP, PAC 9907-23, and PAC 9908-02. An intermediate response was observed in GarnemPVP, Gisela 5PVP, Krymsk 1PVP, Torinel™-AvifelPVP, VSL-2™, and PAC 9904-01. According to the induction of FC-R activity after Fe resupply, genotypes were classified as tolerant, moderately tolerant, or nontolerant to iron-induced chlorosis. These results were compared with SPAD values of plants grown under controlled conditions and in the nursery. Rootstocks that show high induction of FC-R activity also showed high or very high SPAD values in the field.

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Bruce L. Dunn and Jon T. Lindstrom

Controlled reciprocal crosses between Trichostema lanatum Benth. (section Chromocephalum F.H. Lewis) with Trichostema arizonicum A. Gray (section Paniculatum F.H. Lewis) and Trichostema purpusii Brandegee (section Rhodanthum Lewis) were successful in generating the first artificial hybrids in the genus. Crosses where T. lanatum was used as the female were unsuccessful. Leaf and floral morphology among the hybrids was typically intermediate. Female sterility was seen in the T. arizonicum × T. lanatum hybrids, and these hybrids also produced abnormally small, nonviable pollen grains. Propagation procedures are also presented. Although these species may be in different sections, their crossability suggests that they are closely related.

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Mengmeng Gu, James A. Robbins, Curt R. Rom and Hyun-Sug Choi

Net CO2 assimilation (A) of four birch genotypes (Betula nigra L. ‘Cully’, B. papyrifera Marsh., B. alleghaniensis Britton, and B. davurica Pall.) was studied under varied photosynthetic photon flux density (PPFD) and CO2 concentrations (CO2) as indicators to study their shade tolerance and potential for growth enhancement using CO2 enrichment. Effect of water-deficit stress on assimilation under varied PPFD and (CO2) was also investigated for B. papyrifera. The light saturation point at 350 ppm (CO2) for the four genotypes varied from 743 to 1576 μmol·m−2·s−1 photon, and the CO2 saturation point at 1300 μmol·m−2·s−1 photon varied from 767 to 1251 ppm. Light-saturated assimilation ranged from 10.4 μmol·m−2·s−1 in B. alleghaniensis to 13.1 μmol·m−2·s−1 in B. davurica. CO2-saturated A ranged from 18.8 μmol·m−2·s−1 in B. nigra ‘Cully’ to 33.3 μmol·m−2·s−1 in B. davurica. Water-deficit stress significantly reduced the light saturation point to 366 μmol photon m−2·s−1 but increased the CO2 saturation point in B. papyrifera. Carboxylation efficiency was reduced 46% and quantum efficiency was reduced 30% by water-deficit stress in B. papyrifera.

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Sebastian Weissbein, Zeev Wiesman, Yhonathan Ephrath and Moshe Silberbush

Selected superior olive cultivars cultivated on a large scale in various countries in the Mediterranean region were tested in a special saline irrigation experimental plot established in 1997 in the center of the semiarid Israeli Negev area. The plot comprised two subplots containing the same 12 olive cultivars in a mirror image design. One subplot was drip-irrigated with tap water (1.2 dS·m−1) and the second with moderate saline water (4.2 dS·m−1). All cultivation practices applied to the two subplots were similar in terms of fertilization, irrigation, soil leaching, and so on. The present study summarizes the vegetative and reproductive response of the tested olive cultivar trees during the 5 years after they reached maturation and full yield. Evaluation of trunk growth, olive yield, oil percentage, olive oil yield, and fatty acid composition of the oil, sodium and chloride leaf levels, and soil fractions up to 90 cm enabled characterization and comparison of the horticultural performance of the various olive cultivars intensively cultivated with the two tested irrigation treatments. The data clearly showed a significant difference between the tested cultivars in terms of growth, yield, and oil parameters. Grouping the tested cultivars in terms of olive oil production yielded the following three groups: Group A—‘Barnea’, ‘Maalot’, and ‘Picholin’—their average oil yield ranged from 8 to 10 kg/tree; Group B—‘Souri’, ‘Frantoio’, ‘Leccino’, ‘Arbequina’, ‘Picual’, ‘Kalamata’, ‘Koroneiki’, and ‘Picholin di Morroco’—their average oil yield ranged from 5 to 8 kg/tree; and Group C—‘Picudo’—ranged from 3 to 4 kg/tree. Saline irrigation treatment at 4.2 dS·m−1 demonstrated only a low rate of retardation effect on growth or yield of olive trees compared with water at 1.2 dS·m−1 of the same cultivar in each subplot. The data obtained from the present study suggest that efficient productive cultivation of mature olive cultivars in Israeli Negev semiarid conditions, irrigated with moderate saline water, is closely related to proper soil leaching methodology and maintaining the soil electrical conductivity level in the root zone in a range lower than 6 dS·m−1.